Editing Flatfish (section)

==Taxonomy==
Due to their highly distinctive morphology, flatfishes were previously treated as belonging to their own order, Pleuronectiformes. However, more recent taxonomic studies have found them to group within a diverse group of nektonic marine fishes known as the [[Carangiformes]], which also includes [[Carangidae|jacks]] and [[billfish]]. Specifically, flatfish are most closely related to the [[Threadfin|threadfins]], which are now also placed in the suborder Pleuronectoidei. Together, the group is most closely related to the [[archerfish]] and [[Beachsalmon|beachsalmons]] within [[Toxotoidei]]. Due to this, they are now treated as a suborder of the Carangiformes.<ref>{{Cite journal |last1=Girard |first1=Matthew G. |last2=Davis |first2=Matthew P. |last3=Smith |first3=W. Leo |date=2020-05-08 |title=The Phylogeny of Carangiform Fishes: Morphological and Genomic Investigations of a New Fish Clade |url=https://meridian.allenpress.com/copeia/article-abstract/108/2/265/436665/The-Phylogeny-of-Carangiform-Fishes-Morphological |journal=Copeia |volume=108 |issue=2 |pages=265–298 |doi=10.1643/CI-19-320 |issn=0045-8511}}</ref><ref>{{Cite journal |last1=Shi |first1=Wei |last2=Chen |first2=Shixi |last3=Kong |first3=Xiaoyu |last4=Si |first4=Lizhen |last5=Gong |first5=Li |last6=Zhang |first6=Yanchun |last7=Yu |first7=Hui |date=2018-05-25 |title=Flatfish monophyly refereed by the relationship of Psettodes in Carangimorphariae |journal=BMC Genomics |language=en |volume=19 |issue=1 |pages=400 |doi=10.1186/s12864-018-4788-5 |doi-access=free |pmid=29801430 |pmc=5970519 |issn=1471-2164}}</ref>

Over 800 described species are placed into 16 families.<ref name="ReferenceA">{{Cite journal|last1=Campbell|first1=Matthew A.|last2=Chanet|first2=Bruno|last3=Chen|first3=Jhen-Nien|last4=Lee|first4=Mao-Ying|last5=Chen|first5=Wei-Jen|date=2019|title=Origins and relationships of the Pleuronectoidei: Molecular and morphological analysis of living and fossil taxa|journal=Zoologica Scripta|language=en|volume=48|issue=5|pages=640–656|doi=10.1111/zsc.12372|s2cid=202856805|issn=0300-3256|url=https://hal.science/hal-03971070/file/Campbell%20et%20al%202019%20Zool%20Scripta.pdf }}</ref> When they were treated as an order, the flatfishes are divided into two suborders, Psettodoidei and Pleuronectoidei, with > 99% of the species diversity found within the Pleuronectoidei.<ref>{{Cite book|title=Fishes of the world|author-first1=Joseph S. |author-last1=Nelson|author-first2=Terry C. |author-last2=Grande|author-first3=Mark V. H. |author-last3=Wilson|isbn=9781118342336|oclc=958002567|date = 2016-03-28|publisher=John Wiley & Sons }}</ref> The largest families are [[Soleidae]], [[Bothidae]] and [[Tonguefish|Cynoglossidae]] with more than 150 species each. There also exist two monotypic families ([[Paralichthodidae]] and [[Oncopteridae]]). Some families are the results of relatively recent splits. For example, the [[Achiridae]] were classified as a subfamily of Soleidae in the past, and the [[Samaridae]] were considered a subfamily of the Pleuronectidae.<ref name="RandallHawaii">Randall, J. E. (2007). ''Reef and Shore Fishes of the Hawaiian Islands.'' {{ISBN|1-929054-03-3}}</ref><ref name="CopperChapleau">Cooper, J.A.; and Chapleau, F. (1998). ''Monophyly and intrarelationships of the family Pleuronectidae (Pleuronectiformes), with a revised classification.'' Fish. Bull. 96 (4): 686–726.</ref> The families [[Paralichthodidae]], [[Poecilopsettidae]], and [[Rhombosoleidae]] were also traditionally treated as subfamilies of Pleuronectidae, but are now recognised as families in their own right.<ref name="CopperChapleau" /><ref name="Nelson-2006" /><ref name="NGW-2016" /> The [[Paralichthyidae]] has long been indicated to be paraphyletic, with the formal description of [[Cyclopsettidae]] in 2019 resulting in the split of this family as well.<ref name="ReferenceA" />

The [[Taxonomy (biology)|taxonomy]] of some groups is in need of a review.  The last [[monograph]] covering the entire order was [[John Roxborough Norman]]'s ''Monograph of the Flatfishes'' published in 1934. In particular, ''[[Tephrinectes sinensis]]'' may represent a family-level lineage and requires further evaluation e.g.<ref>{{Cite journal|last=Hoshino|first=Koichi|date=2001-11-01|title=Monophyly of the Citharidae (Pleuronectoidei: Pleuronectiformes: Teleostei) with considerations of pleuronectoid phylogeny|journal=Ichthyological Research|volume=48|issue=4|pages=391–404|doi=10.1007/s10228-001-8163-0|bibcode=2001IchtR..48..391H |s2cid=46318428|issn=1341-8998}}</ref>  [[New species]] are described with some regularity and [[undescribed species]] likely remain.<ref name=RandallHawaii/>

===Hybrids===
[[Hybrid (biology)|Hybrids]] are well known in flatfishes. The Pleuronectidae have the largest number of reported hybrids of marine fishes.<ref name=hybridsole>Garrett, D.L.; Pietsch, T.W.; Utter, F.M.; and Hauser, L. (2007). ''The Hybrid Sole Inopsetta ischyra (Teleostei: Pleuronectiformes: Pleuronectidae): Hybrid or Biological Species?'' American Fisheries Society 136: 460–468</ref> Two of the most famous [[intergeneric hybrid]]s are between the [[European plaice]] (''Pleuronectes platessa'') and [[European flounder]] (''Platichthys flesus'') in the [[Baltic Sea]],<ref>[[Food and Agriculture Organization of the United Nations]]: ''[http://www.fao.org/fishery/species/2550/en Platichthys flesus (Linnaeus, 1758).]''. Retrieved 18 May 2014</ref> and between the [[English sole]] (''Parophrys vetulus'') and [[starry flounder]] (''Platichthys stellatus'') in [[Puget Sound]]. The offspring of the latter species pair is popularly known as the hybrid sole and was initially believed to be a valid species in its own right.<ref name=hybridsole/>